Energetic efficiency of two impellers on the same shaft in a cylindrical baffled vessel of high height/diameter ratio

1989 ◽  
Vol 54 (9) ◽  
pp. 2345-2356 ◽  
Author(s):  
Ivan Fořt ◽  
Jiří Hájek ◽  
Václav Machoň
Keyword(s):  
High Speed ◽  
Power Input ◽  
Vessel Diameter ◽  
Diameter Ratio ◽  
Energetic Efficiency ◽  
Turbulent Regime ◽  
Inclined Plane ◽  
Pumping Effect ◽  
Charge Flow ◽  
Turbine Impeller

The paper deals with the experimental study of the indicating particle circulation and the impeller power input in a liquid mechanically agitated with two high-speed impellers (combination of the standard turbine impeller and the six inclined (at 45°) plane blades impeller) on the same shaft in a slender vessel (its height is equal double of the vessel diameter) equipped with four radial baffles at its walls under the turbulent regime of agitated charge flow. By the visual method of the indicating particle it is examined its circulation in the lower part of the system pumping effect of the lower impeller), its circulation in the upper part of the system (pumping effect of the upper impeller), and the exchangeable circulation between the upper and lower part of the system and vice versa. The impeller power input is ascertained from the measured current electricity in the anchor of the direct current driving motor. It follows from the calculated energetic efficiency (the ratio of the cube of the sum of the impeller flow rate numbers and the sum of the impeller power numbers) of the investigated combinations of impellers that the highest value of this quantity is exhibited for two standard turbine impellers on the same shaft and for a combination of the lower standard turbine impeller and the upper impeller with inclined plane blades pumping upwards; slightly less value of the impeller energetic efficiency appears for the combination of two impellers with six inclined plane blades, the upper one pumps liquid upwards and the lower one downwards. For all the configurations the vertical distance of impellers on the same shaft has to be longer than the vessel diameter.

scholarly journals Study of Pumping Capacity of Pitched Blade Impellers

10.14311/380 ◽  
2002 ◽  
Vol 42 (4) ◽  
Author(s):  
I. Fořt ◽  
T. Jirout ◽  
R. Sperling ◽  
S. Jambere ◽  
F. Rieger
Keyword(s):  
Laser Doppler Anemometry ◽  
Radial Profile ◽  
Axial Flow ◽  
Power Input ◽  
Vessel Diameter ◽  
Energetic Efficiency ◽  
Turbulent Regime ◽  
Flat Bottom ◽  
Mean Velocity ◽  
Liquid Suspensions

A study was made of the pumping capacity of pitched blade impellers in a cylindrical pilot plant vessel with four standard radial baffles at the wall under a turbulent regime of flow. The pumping capacity was calculated from the radial profile of the axial flow, under the assumption of axial symmetry of the discharge flow. The mean velocity was measured using laser Doppler anemometry in a transparent vessel of diameter T = 400 mm, provided with a standard dished bottom. Three and six blade pitched blade impellers (the pitch angle varied within the interval a Îá24°; 45°ń) of impeller/vessel diameter ratio D/T = 0.36, as well as a three blade pitched blade impeller with folded blades of the same diameter, were tested. The calculated results were compared with the results of experiments mentioned in the literature, above all in cylindrical vessels with a flat bottom. Both arrangements of the agitated system were described by the impeller energetic efficiency, i.e, a criterion including in dimensionless form both the impeller energy consumption (impeller power input) and the impeller pumping effect (impeller pumping capacity). It follows from the results obtained with various geometrical configurations that the energetic efficiency of pitched blade impellers is significantly lower for configurations suitable for mixing solid-liquid suspensions (low impeller off bottom clearances) than for blending miscible liquids in mixing (higher impeller off bottom clearances).

scholarly journals Power Input of High-Speed Rotary Impellers

10.14311/280 ◽  
2001 ◽  
Vol 41 (6) ◽  
Author(s):  
K. R. Beshay ◽  
J. Kratěna ◽  
I. Fořt ◽  
O. Brůha
Keyword(s):  
Pitch Angle ◽  
High Speed ◽  
Power Input ◽  
Cylindrical Vessel ◽  
Turbulent Regime ◽  
Power Dependence ◽  
Rushton Turbine ◽  
Weak Influence ◽  
Turbine Impeller ◽  
Blade Pitch Angle

This paper presents the results of an experimental investigation of the power input of pitched blade impellers and standard Rushton turbine impellers in a cylindrical vessel provided with four radial baffles at its wall under a turbulent regime of flow of an agitated liquid. The influence of the geometry of the pitched blade impellers (pitch angle, number of blades) and the off-bottom impeller clearance of both high-speed impellers tested on the impeller power input is determined in two sizes of the cylindrical vessel (0.3 m and 0.8 m diameter of vessel). A strain gauge torquemeter is used in the small vessel and a phase shift mechanical torquemeter is used in the large vessel. All results of the experiments correspond to the condition that the Reynolds number modified for the impeller exceeds ten thousand. The results of this study show that the significant influence of the separating disk thickness of the turbine impeller corresponds fairly well to the empirical equations presented in the literature. Both the influence of the number of impeller blades and the blade pitch angle of the pitched blade impeller were expressed quantitatively by means of the power dependence of the recently published correlations: the higher the pitch angle and the number of blades, the higher the values of the impeller power input. Finally, it follows from results of this study that the impeller off-bottom clearance has a weak influence on the power input of the Rushton turbine impeller, but with decreasing impeller off-bottom clearance the power input of the pitched blade impeller increases significantly.

Hydraulic characteristics of turbine impeller

1982 ◽  
Vol 47 (2) ◽  
pp. 421-429 ◽  
Author(s):  
Ivan Fořt ◽  
Jana Malá
Keyword(s):  
Mechanical Energy ◽  
Volumetric Flow Rate ◽  
Vessel Diameter ◽  
Diameter Ratio ◽  
Turbulent Regime ◽  
Hydraulic Efficiency ◽  
Hydraulic Characteristics ◽  
Total Head ◽  
Turbine Impeller

The study concentrates on the determination of hydraulic characteristics (volumetric flow rate, power output, hydraulic efficiency and total head) of a standard, six-blade turbine impeller in a flat-bottomed cylindrical vessel provided with radial baffles at a turbulent regime of agitated liquid. The investigated characteristics are determined by means of a macroscopic balance of mechanical energy of the impeller region expressed in a dimensionless form. The results show that all the hydraulic characteristics investigated, with the exception of the dimensionless impeller total head, are independent of the impeller-to-vessel diameter ratio. The hydraulic efficiency of a standard turbine impeller is about 40%.

scholarly journals Study of the Blending Efficiency of Pitched Blade Impellers

10.14311/276 ◽  
2001 ◽  
Vol 41 (6) ◽  
Author(s):  
I. Fořt ◽  
T. Jirout ◽  
F. Rieger ◽  
R. Allner ◽  
R. Sperling
Keyword(s):  
Pitch Angle ◽  
Theoretical Data ◽  
Vessel Diameter ◽  
Diameter Ratio ◽  
Energetic Efficiency ◽  
Turbulent Regime ◽  
Conductivity Method ◽  
Homogenization Time ◽  
Miscible Liquids ◽  
The Given

This paper presents an analysis of the blending efficiency of pitched blade impellers under a turbulent regime of flow of an agitated low viscous liquid. The conductivity method is used to determine of the blending (homogenization) time of miscible liquids in pilot plant mixing equipment with standard radial baffles. For the given homogeneity degree (98 %) a three-blade pitched blade impeller is tested with various off-bottom clearances, vessel/ impeller diameter ratios and various impeller pitch angles. The experimental results show in accordance with theoretical data from the literature, that the greatest effect on the dimensionless blending time is exhibited by the vessel/ impeller diameter ratio and the impeller pitch angle. The number of total circulations necessary for reaching the chosen homogeneity degree depends on the impeller pitch angle and amounts more than three. Finally, the energetic efficiency of the blending process is calculated. The results of this study show, that the highest energetic efficiency of the three-blade pitched blade impeller appears for the pitch angle a = 24°, the impeller/vessel diameter ratio T/D = 2 and the impeller off-bottom clearance h/D = 1.

Liquid circulation in a cylindrical baffled vessel of high height/diameter ratio with two impellers on the same shaft

1987 ◽  
Vol 52 (11) ◽  
pp. 2640-2653 ◽  
Author(s):  
Ivan Fořt ◽  
Václav Machoň ◽  
Jiří Hájek ◽  
Eva Fialová
Keyword(s):  
High Speed ◽  
Vessel Diameter ◽  
Model System ◽  
Diameter Ratio ◽  
Average Data ◽  
Visual Method ◽  
Liquid Circulation ◽  
Pumping Effect ◽  
Turbulent Flow Regime ◽  
Level Height

The paper deals with the experimental study of the indicating particle circulation in a liquid mechanically agitated with two high-speed impellers (two standard turbine impellers or a lower standard turbine and upper six inclined (at 45°) plane blade impeller) on the same shaft in a slender vessel (its height equals double of the vessel diameter) equipped with four radial baffles at its walls under the turbulent flow regime of agitated charge. The visual method of observation of the indicating particle is used to investigate the model system. Four types of the particle circulation are examined: its circulation in the lower part of the system (pumping effect of the lower impeller), its circulation in the upper part of the system (pumping effect of the upper impeller), and the exchangeable circulation between the upper and lower part of the system and vice versa. It follows from the obtained average data of the above-mentioned circulations that the homogeneous circulation of charge in the whole system is reached providing the vertical distance of the high-speed impellers is equal to at least double of their diameter, their pumping capacities being approximately double compared to those reached in the system with one impeller where the off-bottom liquid level height is equal to the vessel diameter. It follows from the comparison of two arrangements, when the upper high-speed impeller pumps liquid either upwards or downwards, that the homogeneous circulation of all the charge agitated is attained in the first of both the cases compared.

Gas flooding of an inclined blade impeller

1991 ◽  
Vol 56 (3) ◽  
pp. 636-645 ◽  
Author(s):  
Václav Machoň ◽  
Ivan Fořt ◽  
Eva Antošová ◽  
Bohumil Španihel ◽  
Vladimír Kudrna
Keyword(s):  
Relative Size ◽  
Power Input ◽  
Vessel Diameter ◽  
Turbulent Regime ◽  
Gas Flooding ◽  
Rotating Impeller ◽  
Balance Of Forces ◽  
Phase Water ◽  
Input Ratio ◽  
Good Agreement

The conditions are studied in the paper of flooding the six plane blade impeller with blades inclined at the angle of 45° of relative size d/D = 1/3 and relative distance from the bottom of cylindrical vessel H2/D = 1/3 equipped at the wall with four radial baffles of width b/D = 0.1 at the relative vessel filling H/D = 1. The flooding conditions are determined experimentally from the course of dependence of the power input ratio of gassed and ungassed impeller on the flow rate number of air blown into the liquid phase (water) in the vessel. Theoretically, the conditions of the impeller flooding, when it is no more able to disperse air blown into the charge, are determined from balance of forces in the liquid flow leaving the region of rotating impeller acting on the bubbles of rising gas under the turbulent regime of charge flow. The results of the blade impeller frequency of revolutions determined theoretically at its flooding were found to be in good agreement with the experimentally determined values of the frequency of revolutions investigated obtained in the model equipment with vessel diameter D = 290 mm.

Effects of type and number of impellers and liquid viscosity on the power characteristics of mechanically agitated gas—liquid systems

2007 ◽  
Vol 61 (1) ◽  
Author(s):  
R. Adamiak ◽  
J. Karcz
Keyword(s):  
Fluid Flow ◽  
Power Consumption ◽  
High Speed ◽  
Vessel Diameter ◽  
Turbulent Regime ◽  
Relative Power ◽  
Liquid Viscosity ◽  
Power Characteristics ◽  
Liquid Systems ◽  
Inner Diameter

AbstractEffect of the type and number of high-speed impellers installed on a common shaft on the power characteristics was investigated in water and glucose solutions of different concentration. Different configurations of the Rushton or Smith turbines, pitched blade turbines, propeller, and A 315 impeller were tested. Measurements of power consumption were carried out within the transitional and turbulent regime of the fluid flow using the strain gauge method. Baffled agitated vessels with inner diameter of 0.288 m and 0.634 m were used for the experiments. Liquid height in the vessels was equal to the vessel diameter or it was twice higher. The relative power consumption was compared for different configurations of the impellers.

Free Level Effect on the Impeller Power Input in Baffled Tanks

1995 ◽  
Vol 60 (8) ◽  
pp. 1274-1280 ◽  
Author(s):  
Kamil Wichterle
Keyword(s):  
Reynolds Number ◽  
Power Input ◽  
Dimensionless Number ◽  
Simple Correlation ◽  
Mixture Density ◽  
Surface Aeration ◽  
Free Level ◽  
High Reynolds ◽  
Level Effect ◽  
Turbine Impeller

Analysis of extended data on turbine impeller power input in geometrically similar agitated baffled tanks shows that the power number Po is a function of Reynolds number Po = Po*(Re) until the emergence of surface aeration. Though it is usually anticipated that Po* = const in high Reynolds number region, some, whatever weak, function should be taken into consideration in more detailed analysis of the power data even here. In practice, disturbances of level and gas captured in the impeller region play also a significant role, namely in smaller tanks at higher impeller speeds. Decrease of power input can be explained by decrease of gas-liquid mixture density, or in other words by increase of efficient gas holdup eE just in the impeller region. The value eE defined by the relation Po = Po*(Re)/(1 + eE) was determined from the available data. Like other effects of the surface aeration it depends mainly on the dimensionless number Nc = (We Fr)1/4. A simple correlation eE (Nc) is suggested as a correction factor for prediction of impeller power in presence of gas capture.

Energy dissipation rate in a baffled vessel with pitched blade turbine impeller

1991 ◽  
Vol 56 (9) ◽  
pp. 1856-1867 ◽  
Author(s):  
Zdzisław Jaworski ◽  
Ivan Fořt
Keyword(s):  
Energy Dissipation ◽  
Cross Sections ◽  
Mechanical Energy ◽  
Vessel Diameter ◽  
Energy Dissipation Rate ◽  
Mean Velocity ◽  
Agitated Vessel ◽  
Radial Profiles ◽  
Pitched Blade Turbine ◽  
Turbine Impeller

Mechanical energy dissipation was investigated in a cylindrical, flat bottomed vessel with four radial baffles and the pitched blade turbine impeller of varied size. This study was based upon the experimental data on the hydrodynamics of the turbulent flow of water in an agitated vessel. They were gained by means of the three-holes Pitot tube technique for three impeller-to-vessel diameter ratio d/D = 1/3, 1/4 and 1/5. The experimental results obtained for two levels below and two levels above the impeller were used in the present study. Radial profiles of the mean velocity components, static and total pressures were presented for one of the levels. Local contribution to the axial transport of the agitated charge and energy was presented. Using the assumption of the axial symmetry of the flow field the volumetric flow rates were determined for the four horizontal cross-sections. Regions of positive and negative values of the total pressure of the liquid were indicated. Energy dissipation rates in various regions of the agitated vessel were estimated in the range from 0.2 to 6.0 of the average value for the whole vessel. Hydraulic impeller efficiency amounting to about 68% was obtained. The mechanical energy transferred by the impellers is dissipated in the following ways: 54% in the space below the impeller, 32% in the impeller region, 14% in the remaining part of the agitated liquid.

Experimental Study of Turbulent Macroinstabilities in an Agitated System with Axial High-Speed Impeller and with Radial Baffles

1996 ◽  
Vol 61 (6) ◽  
pp. 856-867 ◽  
Author(s):  
Oldřich Brůha ◽  
Ivan Fořt ◽  
Pavel Smolka ◽  
Milan Jahoda
Keyword(s):  
Experimental Study ◽  
Flow Field ◽  
High Speed ◽  
Experimental Results ◽  
Turbulent Regime ◽  
Frequency Of Occurrence ◽  
Visualization Method ◽  
Entire Flow

The frequency of turbulent macroinstability occurrence was measured in liquids agitated in a cylindrical baffled vessel. As it has been proved by preceding experimental results of the authors, the stochastic quantity with frequency of occurrence of 10-1 to 100 s-1 is concerned. By suitable choosing the viscosity of liquids and frequency of impeller revolutins, the region of Reynolds mixing numbers was covered from the pure laminar up to fully developed turbulent regime. In addition to the equipment making it possible to record automatically the macroinstability occurrence, also the visualization method and videorecording were employed. It enabled us to describe in more detail the form of entire flow field in the agitated system and its behaviour in connection with the macroinstability occurrence. It follows from the experiments made that under turbulent regime of flow of agitated liquids the frequency of turbulent macroinstability occurrence is the same as the frequency of the primary circulation of agitated liquid.

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